The Doodle Jump game app for iPhone doesn't take much coordination or thinking for people just looking for a fun way to kill time. A slight tip of the phone to the left and right will have a tiny, green Doodle leaping from platform to platform. If you land on a spring or trampoline, your Doodle buddy will leap past more platforms than a normal jump. And, if you land on the propeller hat or jet pack, your Doodle will fly high without any exertion from you.

But beware of the monsters, UFOs and black holes. Trying to keep the Doodle from missing the platform while trying to shoot the monster (just touch the screen and bullets will begin to fly) requires a little coordination. It'll be easier for a beginner to just jump past the monsters. The UFOs can also be shot before they suck you up, but if you get too close to the black holes, you'll get sucked in fast.

The higher you go, the fewer jumping platforms you'll find. Also, the brown-colored platforms break, blue ones move and white ones disappear after one jump. There are also platforms that turn red and explode.

Tips: The object of the game is to climb, so once a platform disappears from the screen, it's gone for good; also, if you jump off the screen on the right, you'll appear on the left side of the screen.

Once you're used to jumping, try jumping in the dark by swiping the bottom of the screen or typing “;boo”; for your name. There's also a Christmas mode for those who love holidays (type “;snow”; for your name). And, for a different character, type in “;ooga”; for your name.

If you've found a great smart-phone app, share it with those confused by the great app jungle. Tell us in four paragraphs what it does, which phone/service it's made for and whether it's free or has a cost. Send it to .(JavaScript must be enabled to view this email address).